To clarify: I was wondering if there was a chart or conversion trick for figuring out the odometer reading corrected for the tire size. I figured it out on my own; by dividing kilometers by wheel circumference (I realized immediately after I posted that the "wheel factor" in the owner's manual was the circumference in millimetres, and that made it easy), I got the revolutions per kilometer travelled, then I calculated out the odometer reading from that.

For what it is worth, the 26" wheel with 1.5" tires (2030 mm circumference) covers 95.57% of the distance travelled on 700 x 25C tires in the same number of revolutions. In other words, I really rode 67 kilometres yesterday, not 70, and that was what I wanted to know.

(And I measure in metric, since I am in Canada - except for tire sizes which are still in US measurements here. So I don't need to convert feet and inches, thank you.)